Waiting for the snow to melt…
Investigates how alpine pond permanence gradients, interspecific competition, and climate-driven shifts shape amphibian and invertebrate communities in high-elevation wetlands of the Rocky Mountains, drawing on decades of mark-recapture surveys and experimental manipulations.
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High-altitude wetlands in the Gunnison Basin — the shallow ponds, fens, and seasonal pools scattered across subalpine meadows above Gothic — are small in size but outsized in ecological importance. These waters host tightly woven communities of caddisfly larvae, fairy shrimp, zooplankton, midges, and the Arizona tiger salamander (Ambystoma mavortium nebulosum), which sits at the top of the aquatic food web. Because these ponds vary from temporary basins that dry every summer to deeper permanent waters that hold ice-covered water year-round, they form a natural laboratory for asking how the length of time a pond holds water — its pond hydroperiod — shapes which species live where, how they interact, and what ecological work they accomplish.
Several concepts recur throughout this body of research. Interspecific competition refers to the negative effects species exert on each other when they share limited resources such as food or space. Intraguild predation is a more aggressive version of the same idea: members of the same feeding guild eat one another, often when a larger, faster-growing species attacks a smaller competitor. Cannibalism — predation on one's own species — is especially important for tiger salamanders, where large larvae can consume hatchlings. Many wetland insects use case construction, in which caddisfly larvae weave tiny portable shelters out of sedge fragments and silk, both to protect themselves from predators and to manage their environment. Detritus breakdown, the conversion of dead plant material like Carex aquatilis (water sedge) into finer particles and dissolved nutrients, is the engine of these ponds' food webs, and the invertebrates that perform it are sorted into functional feeding groups (shredders, grazers, collectors, predators) according to how they handle food.
2x2 factorial design manipulating temperature and conductivity to test environmental drying cues on caddisfly development and survival. Uses shade man...
Annual capture-recapture surveys over 24 years to track individual survival, growth, reproduction and developmental pathways in a polyphenic salamande...
Systematic collection of water samples from ponds across a hydroperiod gradient for analysis of nitrogen and phosphorus compounds. Samples collected a...
Controlled microcosm experiments measuring invertebrate-mediated breakdown of sedge detritus by quantifying mass loss of coarse and fine particulate o...
Standardized measurements of wing length and dried body mass components under stereomicroscope to quantify adult fitness proxies and assess elevation ...
Fluorometric analysis of ammonia in water samples using working reagent that produces fluorescent compound when reacting with ammonia. Uses quadruplic...
The Environmental Focus Group was asked to provide an opinion on the potential of ski area expansion onto Snodgrass Mountain. We considered the follow...
Technical report (1997). Topics: revegetation, native plant species, ecological restoration. Agencies: Society for Ecological Restoration. Cites 1 ext...
Polyphenisms, alternative morphs produced through plasticity, can reveal the evolutionary and ecological processes that initiate and maintain diversit...
Fitness tradeoffs are a foundation of ecological and evolutionary theory because tradeoffs can explain life history variation, phenotypic plasticity...
Species’ geographic range shifts towards higher latitudes and elevations are among the most frequently reported consequences of climate change. Howe...
Polyphenisms occur when phenotypic plasticity produces morphologically distinct phenotypes from the same genotype. Plasticity is maintained through ...
This dataset contains information on fruit/seed traits of plants in Ranomafana National Park, Madagascar as well as a summary of their fruiting phenol...
This repository hosts the data, R scripts, and Stan models needed to reproduce results and figures from the article Detecting context-dependence in th...
Finally, two life-history concepts are essential. Facultative paedomorphosis is the salamander's option to skip metamorphosis and reproduce while keeping gills, staying aquatic for life — a choice that depends on growing conditions. And climate-induced range shifts describe how warming temperatures and changing snowpack are nudging species upslope, reshuffling which animals encounter one another. Together these concepts frame why a small pond at 3,400 meters can tell us a great deal about how mountain ecosystems work and how they are changing.
Research in these wetlands began with classic zooplankton ecology in the 1970s. Dodson (Dodson, 1974) used cage experiments in an alpine Colorado pond to test the size-efficiency hypothesis and showed that predaceous copepods, not competition alone, structured cladoceran communities — a finding extended by Sprules (Sprules, 1972), who demonstrated that different combinations of invertebrate predators and salamanders produced strikingly different zooplankton assemblages in deep versus shallow ponds only meters apart. Dodson (Dodson, 1972) further estimated that Chaoborus larvae caused roughly 93% of Daphnia mortality in these systems, and Krueger & Dodson (Krueger & Dodson, 1981) revealed that the mere chemical scent of a predator could induce defensive body shapes in Daphnia.
A second foundational thread emerged through Scott Wissinger's work on insect communities and Howard Whiteman's work on salamanders. Wissinger (Wissinger, 1989) and Wissinger & McGrady (Wissinger & McGrady, 1993) demonstrated that dragonfly larvae compete and prey on each other simultaneously, with combined predator effects being non-additive. Wissinger (Wissinger, 1992) introduced size-structured overlap indices showing that body size determines whether two species act mainly as competitors or as intraguild predators. Wissinger et al. (Wissinger et al., 1996) extended this framework to caddisflies, showing that aggressive Asynarchus larvae dominate temporary ponds while Limnephilus dominates permanent ones. Whiteman (Whiteman, 1994) synthesized hypotheses for why tiger salamanders maintain both paedomorphic and metamorphic adult forms, and Harte & Hoffman (Harte & Hoffman, 1989) raised early conservation alarms about salamander population declines in subalpine watersheds.
A consistent picture has emerged across decades of work: pond hydroperiod, predation, and life history interact to determine community structure. Caddisfly distributions along the permanence gradient are not set by physiology alone — Wissinger et al. (Wissinger et al., 2003) showed that some species are confined to permanent waters because their eggs cannot tolerate drying, while species with drought-resistant eggs and rapid growth could in principle live anywhere but are excluded from certain habitats by biotic interactions. Asynarchus, for example, is more vulnerable to salamander predation than Limnephilus (Wissinger, 1999), but compensates through aggressive intraguild predation and cannibalism in temporary ponds (Wissinger et al., 2004). Cases reduce both predation and cannibalism (Wissinger, 2006), and recent work by Romo-Ornelas (Romo-Ornelas, 2025) shows that larvae from ponds with high salamander density build smaller cases and graze on them more often, suggesting subtle, predator-mediated shifts in case-construction strategy.
Tiger salamander ecology has been illuminated by a long-running mark-recapture study at the Mexican Cut Nature Preserve. Cayuela et al. (Cayuela et al., 2024) found that paedomorphs senesce faster and have shorter female lifespans than metamorphs, but paedomorphosis nonetheless dominates this population, occurring 7-19 times more often than metamorphosis. Kirk et al. (Kirk et al., 2024) showed that longer growing seasons favor metamorphosis while light snowpacks and cold overwinter conditions promote paedomorphosis, linking climate directly to life-history outcomes. Kirk et al. (Kirk et al., 2023) found that metamorphs gain body condition over summer more than paedomorphs do, demonstrating climate-mediated fitness trade-offs between the two forms. Cannibalism shapes population dynamics as well: large larvae substantially reduce hatchling survival (Wissinger, 2010), and the salamander population has fluctuated on decadal scales since the 1980s (Wissinger, 2010).
A third major finding is that invertebrates do real biogeochemical work. Caddisfly species differ eightfold in nitrogen excretion and sevenfold in phosphorus excretion (Wissinger, 2018), and they show 13-fold differences in coarse organic matter processing (Balik et al., 2022). Animal-driven nitrogen supply exceeds ecosystem demand in permanent ponds but falls short in temporary ones (Balik et al., 2021), and detritivore activity feeds back to boost algal grazer growth (Wissinger, 2012). Exposed pond sediments during drying release substantial CO2 — 10 to 33 times more per area than the open water surface (DelVecchia et al., 2020) — making these small ponds meaningful players in mountain carbon budgets.
Early work in the 1970s through 1990s established the foundational ecology of predation, competition, and life-history variation in these ponds. Since 2020, the research has shifted sharply toward climate change, range shifts, and the ecosystem-level consequences of species reshuffling. Balik et al. (Balik et al., 2023) used a 30-year survey to show that three successive upslope range expansions of caddisflies have changed which species dominate nutrient supply and detritus processing, yet total ecosystem process rates remained stable — a striking case of functional compensation. A 2020 study (Shepard et al., 2020) found that competition reduces the survival of range-shifting caddisflies at higher elevations but not lower ones, suggesting that resident species can resist upslope invaders. Epele et al. (Epele et al., 2024) extended these questions globally, finding that wetland invertebrate traits track hydroperiod locally while taxonomic composition tracks broad climate.
A second frontier involves salamander biofluorescence — the recently discovered phenomenon in which tiger salamanders emit visible light under blue or ultraviolet excitation. All adults at Mexican Cut fluoresce (Neufell, 2023), intensity increases with sun exposure (Chairez, 2025), and behavioral trials suggest possible but still unclear roles in communication and sexual selection (von der Ohe, 2024); Killian, 2025) (Killian, 2025). Other recent work explores how cattle grazing alters hatchling growth (Miller McShan, 2024), how elevation and snowpack shape paedomorph body size (Bulot, 2025), and how caddisfly case material decomposes at different rates depending on species and detritus type (Madden, 2025).
Many important questions remain. Will functional compensation continue to mask the effects of range shifts, or will further warming push these communities past a tipping point where ecosystem processes change abruptly? How do paedomorphosis and metamorphosis trade off in fitness over a salamander's lifetime under non-stationary climate? What is the biological function of salamander biofluorescence, and does it carry information about health, age, or reproductive status? How will increasing pond drying alter the balance between detritus breakdown in water and carbon release from exposed sediments? And as land use intensifies in the Gunnison Basin, how will cattle, nutrient inputs, and habitat loss interact with climate-driven changes to reshape these small but biogeochemically important wetlands? Addressing these questions will require continued long-term monitoring, comparative work across the elevational gradient, and tighter integration of organismal physiology with ecosystem-scale measurement.
Animal-Driven Nutrient Supply Declines Relative to Ecosystem Nutrient Demand Along a Pond Hydroperiod Gradient (2021). →
Balik et al. (2023). Consequences of climate-induced range expansions on multiple ecosystem functions. Communications Biology. →
Biofluorescence in Polymorphic Tiger Salamanders (2023). →
Biogeochemical characteristics and hydroperiod affect carbon dioxide flux rates from exposed high-elevation pond sediments (2020). →
Bulot (2025). Effects of elevation on salamander life strategies. →
Cayuela et al. (2024). Polyphenism predicts actuarial senescence and lifespan in tiger salamanders. Journal of Animal Ecology. →
Chairez (2025). The effects of natural sun exposure on the intensity and distribution of salamander biofluorescence. →
Dodson (1972). Mortality in a population of Daphnia rosea. Ecology. →
Dodson (1974). Zooplankton competition and predation: an experimental test of the size-efficiency hypothesis. Ecology. →
Elevation alters outcome of competition between resident and range shifting species (2020). →
Epele et al. (2024). A global assessment of environmental and climate influences on wetland macroinvertebrate community structure and function. Global Change Biology. →
Harte, Hoffman (1989). Possible effects of acidic deposition on a Rocky Mountain population of the tiger salamander. Conservation Biology. →
Killian (2025). Biofluorescence in Arizona Tiger Salamanders as an indicator of sexual readiness. →
Kirk et al. (2023). The role of environmental variation in mediating fitness trade-offs for an amphibian polyphenism. Journal of Animal Ecology. →
Kirk et al. (2024). Climate mediates the trade-offs associated with phenotypic plasticity in an amphibian polyphenism. Journal of Animal Ecology. →
Krueger, Dodson (1981). Embryological induction and predation ecology in Daphnia pulex. Limnology and Oceanography. →
Madden (2025). Comparing decomposition rates and detritivore preferences for caddisfly cases versus ambient detritus. →
Miller McShan (2024). The effects of cattle derived nutrients on growth rates of Arizona Tiger Salamander hatchlings in pastureland. →
Romo-Ornelas (2025). Quantifying physiological and behavioral differences in caddisfly larvae. →
Species-specific traits predict whole-assemblage detritus processing by pond invertebrates (2022). →
Sprules (1972). Effects of size-selective predation and food competition on high altitude zooplankton communities. Ecology. →
von der Ohe (2024). Biofluorescence as a Mechanism of Sexual Selection in Ambystoma mavortium nebulosum. →
Whiteman (1994). Evolution of Facultative Paedomorphosis in Salamanders. Quarterly Review of Biology. →
Wissinger (1989). Seasonal variation in the intensity of competition and predation among dragonfly larvae. Ecology. →
Wissinger (1992). Niche overlap and the potential for competition and intraguild predation between size-structured populations. Ecology. →
Wissinger (1999). Foraging trade-offs along a predator-permanence gradient in subalpine wetlands. →
Wissinger (2004). The role of larval cases in reducing aggression and cannibalism among caddisflies in temporary wetlands. →
Wissinger (2006). Predator defense along a permanence gradient. →
Wissinger (2010). Consumptive and nonconsumptive effects of cannibalism in fluctuating age-structured populations. →
Wissinger (2010). Salamander cannibalism. →
Wissinger (2012). Herbivore growth responses to nutrient mobilization by detritivores. →
Wissinger (2018). High interspecific variation in nutrient excretion within a guild of closely related caddisfly species. →
Wissinger et al. (1996). Intraguild predation and cannibalism among larvae of detritivorous caddisflies in subalpine wetlands. Ecology. →
Wissinger et al. (2003). Caddisfly life histories along permanence gradients in high-altitude wetlands in Colorado. Freshwater Biology. →
Wissinger, McGrady (1993). Intraguild predation and competition between larval dragonflies. Ecology. →
Modified gastric-lavage technique to obtain stomach contents for prey identification, enumeration, and biomass/caloric calculations using published co...
Short-term incubation of caddisfly larvae in filtered pond water to measure nitrogen and phosphorus excretion rates under ambient conditions. Five lar...
Larvae offered multiple food choices in aquatic containers with instantaneous behavioral sampling over extended time periods to quantify feeding prefe...
Laboratory aquarium experiment using surgically modified (de-mented) dragonfly larvae to separate behavioral interference effects from direct predatio...
Standardized sampling of large and small benthic invertebrates using D-net sweeps and benthic cores, with zooplankton sampling using mesh nets. Animal...
Organisms are incubated in filtered pond water for one hour to measure nitrogen and phosphorus excretion rates through water chemistry analysis before...
Collection and integration of climate variables from multiple databases including temperature, solar radiation, snow metrics, and topographic factors ...
In-situ measurement of temperature, pH, dissolved oxygen, and barometric pressure at multiple points around each pond during peak photosynthetic activ...
Calculation of body condition metrics (mass/SVL³) and derived fitness proxies including condition-weighted reproductive opportunities for males and es...
Collection and processing of biofilm samples from natural and artificial substrates to quantify biomass, algal content, and nutrient content through A...
Standardized photography protocol using blue light excitation to capture biofluorescence in salamanders under controlled conditions with specific came...
Controlled laboratory experiment comparing survival, growth, and tag retention between PIT-tagged and control salamanders over 90 days to validate tag...
Statistical analysis comparing observed vs. expected species co-occurrence patterns using probabilistic models to identify positive, negative, or rand...
Development and analysis of a seven-dimensional nonlinear differential equation system modeling tiger salamander population dynamics across life stage...
Custom apparatus measuring salamander temperature selection behavior using water-cooled and heated runway with position and body temperature tracking ...
Use of ceramic tiles as standardized substrates for measuring benthic algal biomass via chlorophyll-a extraction and fluorometry. Includes grazed vs u...
Modified gut content analysis method that estimates feeding intensity by counting the proportion of abdominal segments containing food rather than ide...
Controlled behavioral experiments using salamanders in tanks with traps at either end to test preferences for different light stimuli and biofluoresce...
Nutrient addition experiments in benthic substrates and sedge biofilms to measure ecosystem demand through exponential decay models. Measures uptake c...
Classification of ponds into permanent, semi-permanent, and temporary categories based on historical drying patterns and hydroperiod duration from lon...